Introduction to LEGO RCX robotics and Robot Sumo

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Introduction to LEGO RCX robotics and Robot Sumo

• Workshop Day 3
• CJ Chung
• Associate Professor of Computer Science
• Lawrence Technological University

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Workshop Third Day

• Improved Sumo program
• Mini Competition
• Tips and Ideas to improve your Robot!
• Advanced Topics in RCX code (optional)
• Team Pictures
• Planning

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Review Basic Sumo

• Repeat the following forever
• Go forward until the edge
• Backward slightly (in Big block)
• Turn right
• Problems?
• Same behavior all the time!
• Touch sensor was not used

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Improving the Sumo program

• Introduce a random wait value for turning
• Introduce a touch sensor watcher whenever the
  bumper is hit, change the direction

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Improved Sumo Program
Random between 0.5 1.2 seconds
If your opponent is pushing Your back, then
change your direction
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Mini Sumo Competition 1

• Without Unknown Problem
• Every team will compete with every other team
• Team picture time!!!

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Team Picture

• The team picture will be printed on your personal
  certificate
• Please submit the following for each team
• Team name
• Team member first and last name
• Team member grade
• Team member gender

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Mini Sumo Competition 2

• With Unknown Problem
• The robot must wait until touch sensor is pressed
• Wait 5 seconds, then start to move
• You cannot use the previous way using a touch
  sensor watcher! Why? Whenever the touch sensor is
  pressed, the robot will spin

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Better Program for the competition 2

• A nested loop
• Repeat Until that will terminate the loop
  immediately when the termination condition is met

Unknown Problem solution
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Is this a perfect program?

• No, there are still some problems
• One example

• The robot detects the edge line.
• Move backward.
• Turn right around 90 degrees.
• Then the robot must see the outside of
  the ring which is very dark!!!

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Ideas to improve your SumoBot

• Improve (debug) your program!
• Applying Theories learned in Physical Science
• Mass, Newtons laws
• Friction
• Gearing
• Wheel size
• Power level
• Detecting the opponent (can be done later)
• Touch sensor
• IR and light sensor

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Ideas to increase weight of your Robot

• What is the max weight of each division?
• Add more Lego blocks, if you have some at home
• Add Coins, Used Batteries, or others make a
  holder using cardboards
• Put your team name on the robot. An idea make a
  team flag

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Ideas to increase friction of your Robot

• Use rubber bands
• Add more wheels later for Worlds

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Gearing Ideas

• Use gear train to increase gear ratio
• Considering resources, this is not allowed for
  the school qualifier
• The winner from the school qualifier may consider
  this idea later

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Changing Wheels?

• Using bigger wheels
• Considering resources, this is not allowed for
  the school qualifier
• The winner from the school qualifier may consider
  this idea later

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Make sure the Power!

• RCX power level 1 7
• Voltage of your batteries should be around 9V
• How to check the voltage level
• In RIS, click on Settings
• LTU will provide fresh batteries for all the
  teams on the competition day

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Changing the shape of the Robot

• Make it sturdy
• Front part may need some changes (After the
  school qualifier)

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Height of the robot matters?

• Consider the center of gravity

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Ideas using 2 Touch Sensors

• A touch sensor front left
• Another touch sensor front right
• If left sensor is pressed turn left and push
  hard
• If right sensor is pressed turn right and push
  hard
• If both left and right sensors are pressed, push
  straight hard

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What is next? - Meet with your teacher at least
twice before the school qualifier

• Improve your programs
• Add stuff for the max possible weight for your
  robot
• Review what you have learned for the unknown
  problem. If you do not solve the unknown problem,
  you lose automatically
• Signed Media Release form must be ready before
  the qualifying competition date at your school

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Implementing Proximity Sensor to detect opponent
(optional)

• Use a Lego Light sensor and Infrared message
  sending capability of RCX
• RCX is continuously sending IR messages
• Using another light sensor facing forward,
  measure fluctuations in the light intensity that
  is reflected from objects
• The higher the fluctuation, the closer the robot
  is to an object

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How to detect the light fluctuation??

• You need to store previous sensor reading(s)
• Compare with current reading
• If the difference is more than threshold value,
  some thing is in front!

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preval becomes the value of Light 3
preval preval 3
If the current light sensor reading is greater
than (previous value 3), then some thing is
close.
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Sumo with proximity sensor

• Repeat forever
• Scan until find the opponent
• Go forward until the edge
• Backward slightly
• Turn right

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My Blocks (optional topic)
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Opening a saved program (optional)

• Never use File Open! There is a bug involving
  MyCommands
• Use Main Menu Program Vault